It is proposed to evaluate, over a wide range of dosages, the effect of 25 potentially toxic chemicals on murine sperm morphology and chromatin structure using light and electron microscopy combined with flow cytometric analyses. The incidence of chemically-induced abnormally-shaped sperm will be compared with the 1) population chromating thermal denaturation (at index) profile developed by the applicants and 2) accessibility of sperm chromatin to various fluorescent probes of chromatin structure. It is anticipated that these studies will lead to a determination of whether alterations in sperm shape or chromat instructure provides the most useful dosimeter of response to hazardous chemical agents.